The people being slashed etc are usually civilians. They are like the great grandfathers of Daesh/Isis although Kurds would have been part of them then. The costumes (some seem a bit "Sunday best") could easily go to the period of the Greek and Armenian massacres/genocide in the 20th c and they would often pose with weapons of an antique nature but I would assume they used contemporary weapons and more swords. They were paid by plunder so gamers having them as cavalry in heroic charges seems unlikely in reality. A corpse doesn't cart much plunder.

Actually, these savage fellows are only accurate for the period through the 1880's or thereabouts. The Ottomans tired of the bashi-bazouks' antics after the debacle in the Balkans plus the Egyptians' bad experiences with them in the Sudan in the 1880's and they disappeared by 1890 or so. What replaced them in Eastern Turkey wasn't much better - it were the Hamidiye units of irregular Kurdish or Turkmen cavalry, uniformed in either civilian dress or Caucasian-style beshmet coats and fur papakha caps. They had modern rifles and, in World War I, machine guns, that were mostly used to massacre Armenians, Anatolian Greeks and Assyrians - both the handfuls of rebels or insurgents and the much greater numbers of civilians.